Figure 2.

(A)Twenty-four-month-old rats (□) were significantly impaired in comparison with 6-month-old rats (○) during place learning. Aged rats (A, Inset) showed greater heterogeneity than young rats (Y). (B) There was no reliable difference between 24-month-old rats (□) and 6-month-old rats (○) during acquisition of the transfer task. During the probe trial (Inset), the subgroup of aged rats that performed outside the range of young rats on the original spatial task (AI, aged impaired; n = 15) also showed significantly less spatial bias than either aged rats that performed within the range of the young rats (AU, aged-unimpaired; n = 12) or young rats (Y, n = 13).